1. Field of the Invention
The present invention relates to a gas pressure-reducing valve. In particular, it relates to an improvement of a gas pressure-reducing valve, wherein a pressure-reducing chamber for generating a gas pressure that acts on one surface of a diaphragm is formed within a valve housing that clamps the peripheral edge of the diaphragm, a valve body that can sit on a valve seat having in its central part a valve hole communicating with the pressure-reducing chamber is fixed to one end of a valve stem penetrating the valve hole in an axially movable manner, the other end thereof being connected to the central part of the diaphragm, and a spring biasing the diaphragm in a direction that detaches the valve body from the valve seat is housed in a spring chamber formed within the valve housing, the spring chamber facing the other surface of the diaphragm.
2. Description of the Related Art
Conventionally, such a gas pressure-reducing valve is already known in, for example, Japanese Patent Application Laid-open No. 11-270718, wherein a valve housing is formed from a body and a cover fastened to the body, and the peripheral edge of a diaphragm is clamped between the body and the cover.
In the above-mentioned conventional arrangement, since a pressure-reducing chamber is formed between one surface of the diaphragm and the body, the body structure surrounding the pressure-reducing chamber becomes complicated, thereby raising the possibility that the machining precision might be degraded. Furthermore, when the diameter of the diaphragm is made small in order to satisfy a need for reducing the dimensions of the gas pressure-reducing valve, it becomes necessary to make small the diameter of the pressure-reducing chamber facing said one surface of the diaphragm, thereby changing the flow characteristics of the gas pressure-reducing valve and bringing about a situation where the gas pressure of the pressure-reducing chamber might fall below the target control pressure by a large amount.
The present invention has been carried out in view of the above-mentioned circumstances, and it is an object of the present invention to provide a gas pressure-reducing valve that can enhance the machining precision by simplifying the body structure and determine the diameter of the pressure-reducing chamber regardless of the diameter of the diaphragm.
In order to accomplish the above-mentioned object, in accordance with a first aspect of the present invention, there is proposed a gas pressure-reducing valve that includes a pressure-reducing chamber for generating a gas pressure that acts on one surface of a diaphragm; the pressure-reducing chamber being formed within a valve housing that clamps the peripheral edge of the diaphragm; a valve body that can sit on a valve seat having in its central part a valve hole communicating with the pressure-reducing chamber; a valve stem penetrating the valve hole in an axially movable manner wherein one end of the valve stem is connected to the central part of the diaphragm and the other end of the valve stem is fixed to the valve body; and a spring biasing the diaphragm in a direction that detaches the valve body from the valve seat, the spring being housed in a spring chamber formed within the valve housing and the spring chamber facing the other surface of the diaphragm. In this gas pressure-reducing valve, the valve housing is formed by conjoining a body, a partition, and a cover, the body being provided with the valve seat, the partition forming the pressure-reducing chamber between itself and the body and forming a pressure action chamber between itself and one surface of the diaphragm, and the cover forming the spring chamber between itself and the other surface of the diaphragm and clamping the peripheral edge of the diaphragm between itself and the partition, and wherein the partition includes a through hole for allowing the valve stem to run through in an airtight and axially slidable manner and a communicating hole for providing communication between the pressure action chamber and the pressure-reducing chamber.
In accordance with the above-mentioned arrangement of the first aspect, the peripheral edge of the diaphragm is clamped between the cover and the partition interposed between the cover and the body, the pressure-reducing chamber is formed between the partition and the body, and the pressure action chamber that communicates with the pressure-reducing chamber is formed between one surface of the diaphragm and the partition. It is therefore possible to simplify the structure of parts of the body facing the pressure-reducing chamber thereby enhancing the precision with which the body is machined and enabling the partition to be machined easily in a state where it is separated from the body. Furthermore, although the diameter of the pressure action chamber changes in accordance with changes in the diameter of the diaphragm, the diameter of the pressure-reducing chamber which is separated from the pressure action chamber by the partition can be determined independently of a change in the diameter of the diaphragm. Even when the diameter of the diaphragm is made small in order to satisfy a need for reducing the dimensions of the gas pressure-reducing valve, it is unnecessary to decrease the diameter of the pressure-reducing chamber, thereby avoiding the occurrence of any change in the flow characteristics that would cause the gas pressure of the pressure-reducing chamber to fall below the target control pressure by a large amount. Moreover, since the gas pressure of the pressure-reducing chamber does not directly act on said one surface of the diaphragm, it is possible to prevent an excessive load from being imposed on the diaphragm when the gas pressure of the pressure-reducing chamber changes greatly, thereby protecting the diaphragm.
Furthermore, in accordance with a second aspect of the present invention, in addition to the above-mentioned first aspect, there is proposed a gas pressure-reducing valve wherein the body has a slide bore so that the valve body is slidably fitted in the slide bore. In accordance with the above-mentioned arrangement, the axial movements of the valve body and the valve stem are supported at two points; on the inner face of the slide bore of the body; and on the inner face of the through hole provided on the partition, thereby preventing the valve body and the valve stem from tilting and ensuring reliable opening and closing operations of the valve body.
Furthermore, in accordance with a third aspect of the present invention, in addition to the above-mentioned arrangement of the first aspect, there is proposed a gas pressure-reducing valve wherein the diaphragm, the valve stem and the valve body are assembled to the valve housing so that, when the diaphragm is in its natural state without any external force acting on it, the valve body is detached from the valve seat.
In accordance with the above-mentioned arrangement of the third aspect, when the diaphragm is assembled to the valve housing in its natural state without any external force acting on it, the valve body is detached from the valve seat, and when the diaphragm bends so as to seat the valve body on the valve seat in response to the action of the gas pressure of the pressure-reducing chamber, the diaphragm bends toward the spring chamber side so as to be in a state in which the diaphragm exerts a resilient force in the same direction as the direction of the spring force, that is to say, opposite to the direction in which the gas pressure of the pressure-reducing chamber closes the valve. When the valve body is detached from the valve seat to a great extent so as to increase the gas flow, the resilient force exerted by the diaphragm against the force of the gas pressure of the pressure-reducing chamber in the direction which closes the valve becomes small. It is thereby possible to minimize any adverse effect on the responsiveness resulting from the resilient force exerted by the diaphragm, and even when the gas flow increases, the pressure of the pressure-reducing chamber is not controlled at a lower value.
Furthermore, in accordance with a fourth aspect of the present invention, in addition to the arrangement of the third aspect, there is proposed a gas pressure-reducing valve wherein the diaphragm is formed integrally from a ring-shaped outer peripheral seal part clamped by the valve housing, a valve stem connecting part connected to one end of the valve stem, and a flexural part having a transverse cross section that protrudes toward the spring chamber side and disposed inward relative to the outer peripheral seal part so that, when the diaphragm is in its natural state, the inner periphery of the flexural part is offset toward the pressure-reducing chamber side by a predetermined amount relative to the outer periphery of the flexural part.
In accordance with the arrangement of the fourth aspect, when the diaphragm, in its natural state, is assembled to the valve housing, the inner periphery of the flexural part of the diaphragm, that is to say, the central part to which the valve body is connected via the valve stem is offset toward the pressure-reducing chamber side relative to the outer periphery of the flexural part. It is easy to achieve a state in which, when the diaphragm in its natural state is assembled to the valve housing, the valve body is detached from the valve seat, thereby making assembly of the diaphragm easy.
Furthermore, in accordance with a fifth aspect of the present invention, in addition to the arrangement of the first aspect, there is proposed a gas pressure-reducing valve further including a leaf spring that is in frictional contact with the inner face of a cylindrical part forming a part of the valve housing thereby applying a sliding resistance to the diaphragm, wherein the leaf spring is formed from a bottomed cylindrical cup and a plurality of leaves connected integrally with the open end of the cup so as to be in resilient sliding contact with a plurality of points spaced at equal intervals in the circumferential direction on the cylindrical part, the closed end of the cup being interposed between the spring housed in the spring chamber in a coiled form and a retainer mounted on the central part of the diaphragm on the spring chamber side, and the spring chamber being formed in the cylindrical part.
In accordance with the arrangement of the fifth aspect, the leaf spring applies sliding resistance to the diaphragm against the self-induced vibration of the coil spring as a result of the plurality of leaves of the leaf spring making resilient sliding contact with the inner face of the cylindrical part, which is a part of the valve housing. Even when the diameter of the cylindrical part decreases as the diameter of the diaphragm decreases, the contact areas between the leaf spring and the cylindrical part do not change. The level of sliding resistance therefore does not increase as the dimensions of the gas pressure-reducing valve reduce. Furthermore, the level of sliding resistance due to the resilient sliding contact between the leaf spring and the cylindrical part does not change as the temperature changes. It is therefore possible to apply a stable sliding resistance against the self-induced vibration of the coil spring regardless of a reduction in the dimensions of the diaphragm and a change in the temperature, thereby preventing any degradation in the responsiveness of the gas pressure-reducing valve. Moreover, since the plurality of leaves are supported by the cup having a comparatively high rigidity, when assembling the leaf spring to the valve housing, breakage, etc. of the leaves can be avoided, thereby enhancing the ease of assembly.
Furthermore, in accordance with a sixth aspect of the present invention, in addition to the arrangement of the first aspect, there is proposed a gas pressure-reducing valve wherein the spring chamber housing the spring in a coiled form is formed within a cylindrical part forming a part of the valve housing, the cylindrical part being provided with an end wall on the side opposite the diaphragm; an adjustment screw is screwed into a support tube arranged coaxially within the cylindrical part and connected to the end wall, the adjustment screw in accordance with its axial position adjusting the spring load of the spring; the support tube is provided coaxially with a small diameter hole on the axially inner side and a large diameter hole on the axially outer side, a female thread being cut into at least one part of the large diameter hole; the adjustment screw is formed by coaxially connecting a small diameter shaft part and a large diameter shaft part, the small diameter shaft part being fitted in the small diameter hole and having mounted on its outer face an annular seal that makes resilient contact with the inner face of the small diameter hole, the large diameter shaft part having on its outer periphery a male thread mating with the female thread and on its outer end an engagement recess that can engage with a rotating tool, and the axial position of the adjustment screw being set so that the outer end of the large diameter shaft part is positioned inward relative to the outer face of the end wall; and a recess is formed in the outer end part of the large diameter hole employing the outer end of the large diameter shaft part as a closed end of the recess, the recess being filled with a filler that can be solidified.
In accordance with the arrangement of the sixth aspect, merely adjusting the axial position of the adjustment screw by screwing it into the support tube can adjust the spring load of the coil-form spring, thereby reducing the number of components as well as the number of assembly steps. The support tube is provided coaxially with the small diameter hole on the inward side and the large diameter hole on the outward side. The adjustment screw is fitted into the small diameter hole and has on its forward end the small diameter shaft part having mounted on its outer face the annular seal in resilient contact with the inner face of the small diameter hole. It is therefore possible to minimize any damage to the seal caused by the female screw provided on the inner face of the large diameter hole when the adjustment screw is inserted into the support tube. Since the adjustment screw is screwed into the support tube until the outer end of the adjustment screw reaches a position that is inward relative to the outer face of the end wall, the adjustment screw does not project out of the outer face of the end wall, thereby contributing to a reduction in the dimensions of the gas pressure-reducing valve. Furthermore, since the recess is formed in the outer end part of the large diameter hole, the recess employing the outer end of the large diameter shaft part of the adjustment screw as its closed end, and the recess is filled with the filler, solidifying the filler can gain the effects of preventing the adjustment screw from rotating and of preventing erroneous operation while at the same time requiring neither a lock nut nor a cap. In particular, the filler entering the engagement recess in the outer end part of the adjustment screw can yet more reliably prevent the adjustment screw from rotating.
Furthermore, in accordance with a seventh aspect of the present invention, in addition to the arrangement of the sixth aspect, there is proposed a gas pressure-reducing valve wherein the female thread is cut into the large diameter hole, one part of the female thread facing the recess. In accordance with the above-mentioned arrangement, since the filler enters the threads of the female thread, the filler can be reliably retained within the recess and can also efficiently penetrate into the part where the male thread of the adjustment screw and the female thread of the large diameter hole are screwed together, thereby yet more reliably stopping the adjustment screw from rotating.
The above-mentioned object, other objects, characteristics and advantages of the present invention will become apparent from explanations of preferred embodiments that will be described in detail below by reference to the appended drawings.